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Keil RTX and bootloading

Johan Moraal
Note: This was originally posted on 25th January 2011 at http://forums.arm.com

Hi all.

I've recently written a secondary bootloader for NXP LPC17xx devices. The design is relatively simple: All our products have embedded serial flash connected with an SPI bus to the micro. The user application is responsible to load a binary image onto the serial flash. When the bootloader starts, it checks the serial flash for a binary image. If one is not found, it jumps to the user application. If one is found, it verifies the integrity of the image by doing a CRC check. If the check passes it begins to update the LPC's flash from the binary image on the serial flash.

I've confirmed that the bootloader application is working properly. Firstly I checked the LPC's flash with a ULINK Pro and made sure the bootloader is not accidentally overridden. Then I uploaded a small application that reads and verifies a large chunk of flash and blinks a led. All these tests succeeded and I'm confident my bootloader works properly.

The problem arises when I try to upload an application which uses the Keil RL-ARM real time OS. When I upload this type of application, nothing happens. I traced the problem with a ULINK and I found that the trace stops at SVC_Handler in startup_LPC17xx.s.

All our RL-ARM based applications run in privileged mode. I know the RTOS uses SVC to access hardware etc in privileged mode.

Is there something I should do in the bootloader in order to support RL apps?
  • Arm Employee Badge
    Note: This was originally posted on 25th January 2011 at http://forums.arm.com

    Hi there,

    The Keil RTX Kernel should contain the require SVC handler. For some unknown reasons, the SVC vector in your compiled image might be  pointing to the dummy SVC handler in the startup code rather than the OS kernel.  You might need to check your compile and linking options to see if anything can affect it.
    The dummy SVC handler in the startup code should be declared as [WEAK], which mean it can be overridden by a real SVC handler is it is presented. You can also try remove the dummy SVC handler in the startup code to see if it can solve the problem.

    Are you using the source code version or precompiled RTX kernel library?
    If using the source version, make sure HAL_CM3.c is included in the project.
    This contains the "SVC_Handler".

    regards,
    Joseph
  • Note: This was originally posted on 25th January 2011 at http://forums.arm.com

    I've found my problem:
    in the file system_LPC17xx.c I found this:

    //  Set Vector table offset value
    #if (__RAM_MODE__==1)
      SCB->VTOR  = 0x10000000 & 0x3FFFFF80;
    #else
      SCB->VTOR  = 0x00000000 & 0x3FFFFF80;
    #endif

    this obviously sets the VTOR to the incorrect location. It's merely a coincidence that the application running priveledged mode had the above code and the one running unpriveledged mode did not have it.. SVC is the first IRQ in my RTX app
  • Note: This was originally posted on 21st August 2011 at http://forums.arm.com

    Johan

    I have a booloader running on 0x00000000 and another application starting 0x00002000, where the first read the external
    flash and copy the firmware upgrade to 0x00002000 and jump the pc for it.

    So What do I need modify on

    startup_lpc17xx.s
    core_cm3.h
    system_lpc17xx.c
    lpc17xx.h

    In order to :

    - Use the 0x00002000 application on normal and debug mode, avoiding undesired writes on bootloader region.
    - Remap all vector address to run the application normally.

    Should you explain, what the correct order of code execution before the PC go to the main ?

    Regards.

    Jean Fernandes
  • in reply to Johan Moraal

    Thank you so much for posting this. I really can't understand why it is set to 0 in this file. Took me 2 days to find why the boot code ran, the main app ran but I couldn't start the RTOS. Of course it's because the vectors were in the wrong place - even though I had set them to the right place in the boot code!